Reproducibility of early and late asthmatic responses to allergen challenge in a large group of asthmatics

Abstract

The specific bronchial provocative test (sBPT) coupled with allergen is used to investigate asthma. Very few studies have examined the reproducibility of responses to allergen challenge. The aim of this study was to measure the reproducibility of PD20FEV1allergen and late asthmatic response (LAR) in 53 asthmatics and to relate the reproducibility to the time interval between two allergen challenges.Fifty-three atopic asthmatics performed two allergen challenges not less than 2 and not more than 26 weeks apart. Randomly, 19 subjects were assigned to a short-interval group (14–35 days between the two tests) and 34 to a long-interval group (40–180 days). In each challenge, the PD20FEV1was sought for and the maximum % fall in FEV1from 3 to 7 h after the allergen challenge was evaluated as a measurement of magnitude of the LAR.High intraclass correlation coefficients (RI) were found for both PD20FEV1(RI= 0·78) and LAR (RI= 0·77) in all subjects. PD20FEV1allergen showed a high RIin the long-interval group (RI= 0·80), but a low RIin the short-interval group (RI= 0·63). In contrast LAR showed a lower RIin the long-interval group (RI= 0·68) than in the short-interval group (RI= 0·77). Moreover, the RIfor PD20FEV1was particularly low in subjects with a dual pattern to the allergen challenge and a short interval between the two allergen challenges.Our study confirmed that asthmatic responses induced by allergen challenge have a good reproducibility. Moreover, we have demonstrated that the interval between two allergen challenges can determine a change in reproducibility in asthmatic responses induced by allergen challenge.